Submerged combustion is a method of heating whereby hot products of combustion are forced through a solution to heat the solution. The heat exchange occurs directly between the hot products of combustion and the solution. In a submerged combustion system, the hot combustion products are generated by a flame which is typically fed by a combination of air and natural gas. The flame does not come into contact with the solution. This technology differs from conventional heat exchange methods such as immersion tube heating where the heat exchange is indirect and the products of combustion are exhausted directly to the atmosphere, rather than being forced through the solution. Submerged combustion can be utilized to heat liquids with overall system efficiency greater than 90%. Conventional hot water boiler heating systems have an efficiency of about 80% while immersion tube systems have an efficiency of about 70%.
In applications where separation of components by distillation or absorption is required, submerged combustion can be applied to provide liquid temperatures up to about 195.degree. F.
In addition to high efficiency, submerged combustion systems are advantageous because they maintain a uniform temperature throughout the solution in which the submerged combustion is conducted. The hot combustion products keep the solution in constant agitation. Submerged combustion systems are also suitable for heating contaminated liquids. Expenses are usually lower because the submerged combustion can be conducted in a tank which need not be pressurized. Unlike boiler heating applications, a certified operating engineer is not required to operate a submerged combustion system.
Typical industrial applications for submerged combustion systems include: (a) natural gas processing plants--effluent pond heating; (b) municipal effluent holding and treatment ponds--maintenance of pond temperatures to ensure continuous high level of biological degradation especially in regions that experience extreme seasonal temperature changes; (c) aggregate wash plants--heating aggregate wash water at concrete batch plants; (d) log ponds and conditioning chests--heating log ponds and conditioning vats in plywood, veneer, orientated strand board (OSB), waferboard, chopstick plants; (e) pulp and paper--mill water intake protection against freezing, white water solution heating; (f) heap leach mining--heating of barren solutions for ore extraction in heap leaching operations; (g) wet potash mining--heating of barren brine solution to maximize solubility and recovery of potash in flooded potash mines; (h) coal thawing for conveying; (i) carpet and fabric manufacturing--heating of bulk carpet and fabric dyes; (j) cogeneration--evaporation of waste water to recover water treatment chemicals in plants with zero effluent discharge; and (k) industrial processes--processes requiring large volumes of hot water or non-flammable liquids, or processes requiring a direct source of heat for distillation or absorption.
Typical commercial applications for submerged combustion systems include: (a) swimming pool heating--institutional and residential; (b) fish hatcheries--fresh water heating; (c) commercial laundries--wash water heating; (d) automotive car washes; (e) snow disposal; and (f) food processing plants.